Adams

Answer 1 : Because camber gain is helpful in performance car as it tend to change while car is accelerating, braking , cornering depend on what type of geometry is selected. For example while cornering negative camber helps to increase traction and for straight run zero camber is desired. Again suspension in itself is a compromise in order to achieve something you loose many other things.

Answer 2 : If dynamic camber is less than 1 degrees while cornering then in order to negotiate it 1 degrees of static camber can be set. If dynamic camber more than 2 degrees while cornering then we cannot 2 degrees of static camber because it will ruin tyres.

Answer 3 : I would strongly go with double wishbone if it is has to be from handling perspective because with double wishbone it is easy to control camber while cornering (Negative camber). Outer tyre while cornering gains negative camber so this translate to good stability as the tyres on the outside maintain more contact with road surface. So, handling performance also increases. But in a case of MacPherson strut things change, small camber change with vertical movement of suspension could make tyres to have lesser contact with road surface during cornering this could reduce handling abilities of vehicle.